A cardboard-supported structure might sound like a truly lousy place to own a house cat (break out those extra scratching posts), but architect Shigeru Ban favors the material as cheap, easy to work with and readily available -- a source of endless new architectural and structural engineering opportunities. These qualities mesh well with Ban's humanitarian efforts, including the cheap temporary housing he designed for Rwandan refugee camps [sources: Corkill; Etherington].
To Ban, whatever green qualities his structures possess is accidental; he regards the green movement as another passing fashion. But when Hannover Expo 2000 (a world's fair) asked him to keep with its environmental theme, he rose to the occasion. Seeking to minimize industrial waste, he designed the Japan Pavilion to reuse or recycle the most material possible. Its undulating tunnel arch -- a grid of gently swooping paper tubes covered by a paper membrane and supported by pulling cables -- measured 242 feet long, 82 feet wide and 52 feet high (73.8 x 25 x 15.9 meters) and featured a wooden arch for strength at each end [source: Shigeru Ban].